Charles S. Johnson

During the '20s, Charles S. Johnson, a civil engineer from the University of Illinois, developed and patented a number of aggregate storing and batching designs for the booming highway industry. Then in 1931, he turned his attention to what would eventually be known as one of the most difficult and daring projects ever undertaken - construction of the Hoover Dam.

The project demanded high - volume, low-cost concrete, and Johnson responded with the first-ever fully automatic plant for mass concrete. His design featured a multi-weigh hopper and scale system with a tilting mixer, which accelerated the speed of both batching and mixing operations. When the dam was complete, the plant would yield nearly 4.5 million cubic yards of concrete. Johnson's innovations at Hoover Dam set the criteria for hydroelectric plants on an international scale, serving as guidelines for the U.S. Corps of Engineers and the Bureau of Reclamation.